1. Field of the Invention
The present invention relates to a method for regenerating a particulate filter of an internal-combustion engine and also relates to an internal-combustion engine which performs the method.
2. Description of the Prior Art
The emissions of diesel-powered internal-combustion engines contain a considerable amount of particulate and are subject to stringent anti-pollution regulations. Diesel-powered internal-combustion engines are equipped with a particulate filter so as to retain the particulate and comply with given anti-pollution parameters laid down by the existing regulations. The capacity of the particulate filter is limited and periodically the particulate filter must be regenerated by means of cycles for burning off the particulate in the filter. Combustion of the particulate produces carbon dioxide which is expelled from the filter together with the exhaust gases and in effect ensures cleaning of the particulate filter. The need to perform regeneration of the particulate filter depends on the running speed of the internal-combustion engine and the running speed transients. In fact, particular operating conditions of the internal-combustion engine give rise to temperatures of the exhaust gases able to initiate combustion of the particulate retained by the filter and, at the same time, produce the supply of oxygen needed to perform combustion and partially free the filter of the particulate. However, the running speeds and transients which give rise to the abovementioned conditions are not maintained for a sufficient amount of time to cause complete regeneration (cleaning) of the particulate filter and consequently the temperature and excess air conditions of the exhaust gases must be determined and maintained for a sufficient amount of time in order to perform complete regeneration (cleaning) of the particulate filter.
The temperature needed to trigger combustion of the particulate within the particulate filter is provided by means of post-combustion in the exhaust-gas pipe of excess air and fuel supplied in the exhaust-gas pipe.
Post-combustion is performed upstream of the particulate filter along the exhaust-gas pipe and involves the supply of fuel to this point at an average pressure of more than 6 bar. This means that the vehicle must be equipped with a fuel pump able to supply the fuel upstream of the particulate filter in any operating condition of the internal-combustion engine.